1. Field of the Invention
The invention relates to an inert gas electric arc welding process and to a torch for use in the process.
2. Discussion of the Background
Electric arc welding is carried out in most industrial fields, especially the aerospace, aeronautical and nuclear industries, and is often performed by an automatic welding system.
In TIG arc welding processes an electric arc is produced between a stationary refractory electrode and two metal articles which are to be welded together, and a melt pool is formed by transfer of energy from the arc into the material of the metal articles. The arc and the melt pool are protected by surrounding them with an inert gas. The welding operation is performed progressively either by moving the articles past the stationary arc or by moving the arc over the articles, which remain stationary. However, because of the movement of the arc relatively to the articles, the melt pool has a temperature spread which may cause weld defects. These defects can be blowholes formed by gases trapped in the weld, or an unsatisfactory surface texture of the weld bead. Blowholes have a particularly adverse effect on the mechanical strength of the weld since they produce porosities which weaken the weld. These weld defects are even worse when the weld is formed between two articles made of different metals or between very thick articles.